I. Field
The present disclosure relates generally to communication, and more specifically to techniques for controlling the transmit power of a user equipment (UE).
II. Background
Wireless communication systems are widely deployed to provide various communication content such as voice, video, packet data, messaging, broadcast, etc. These wireless systems may be multiple-access systems capable of supporting multiple users by sharing the available system resources. Examples of such multiple-access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal FDMA (OFDMA) systems, and Single-Carrier FDMA (SC-FDMA) systems.
A wireless multiple-access communication system can communicate with multiple UEs on the downlink and uplink. The downlink (or forward link) refers to the communication link from the Node Bs to the UEs, and the uplink (or reverse link) refers to the communication link from the UEs to the Node Bs. Multiple UEs may simultaneously receive data on the downlink and/or transmit data on the uplink. This may be achieved by multiplexing the transmissions on each link to be orthogonal to one another in time, frequency and/or code domain. On the uplink, complete orthogonality, if achieved, results in the transmission from each UE not interfering with the transmissions from other UEs at a receiving Node B. However, complete orthogonality among the transmissions from different UEs is often not realized due to channel conditions, receiver imperfections, etc. The loss of orthogonality results in each UE causing some amount of interference to other UEs communicating with the same Node B. Furthermore, the transmissions from UEs communicating with different Node Bs are typically not orthogonal to one another. Thus, each UE may also cause interference to other UEs communicating with nearby Node Bs. The performance of each UE is degraded by the interference from other UEs in the system.
There is therefore a need in the art for techniques to control the transmit power of a UE to achieve good performance for that UE while reducing interference to other UEs.